Reaction-drives, also known as pressure-jet and tip-jet systems have been used successfully in the past to provide rotor power for helicopters. Reaction drive helicopters differ from conventional helicopters in that the rotor power is provided by the thrust of jets mounted at the blade-tips. This eliminates the mechanical transmission systems of conventional helicopters leading to a much lighter aircraft, requiring less energy to move. Reaction drive helicopters have a number of variants which, for the purposes of this invention, are considered to be divided into a first type in which air or gasses are directed through the blades and out a nozzle at the blade tip, and a second type in which a motor is positioned at the blade tip. The first type is typically differentiated on the basis of the air or gas temperature exiting through the jet nozzle at the tips of the helicopter blades. Usually these are labeled hot, warm or cold cycle tip-jet systems and are generated remotely from the blade tip. It is recognized that reaction drive helicopters are part of a larger group of related propulsion units that are generally termed reactive jet drive rotor systems. This larger group encompasses other helicopter rotor tip driven systems including the second type, in which motors such as turbojets, rockets, ramjets, pulse jets and other combustion engines attached to the blade tips have been used to provide rotor power for lifting and forward flight purposes.
While the various systems can be effective, none are used extensively because the energy saved by the reduced weight, is more than offset by inefficiencies in the generation of thrust at the blade tip in the instances of the second type, and losses to air/gasses velocities and pressures during transmission of the air/gasses to the nozzle at the blade tip in the first type. For purposes of this invention, only the first type will be of interest in this description. The pressure loss along the air/gas flow path from the load compressor or engine bleed point to the blade tips is extremely important to reaction drive helicopters. Pressure losses directly contribute to reductions in the system efficiency. It is essential that the pressure losses are reduced to minimal levels. Most of the significant pressure losses occur when the air/gas flows change direction. Another reason care has to be taken to minimize pressure loses, is because reaction drive helicopters use a pneumatic transmission that is less efficient than the conventional mechanical system.
One of the primary areas of concern is the transition of the gases from a vertical direction, moving vertically up the rotor mast, to a generally horizontal direction along the rotor blades. The transition occurs in the rotor hub, and can result in a large pressure drop when the flows turn and divide at a multiple branched “Tee Junction in the rotor hub.”
It would be highly advantageous, therefore, to remedy the foregoing and other deficiencies inherent in the prior art.
It is an object of the present invention to reduce the energy losses incurred by the air/gasses transmitted into the blades of the rotor.